To know (something) without having to thinkintellectually (such as knowing the number of objects in a collection without needing to count them: see subitize).

1961, Robert A. Heinlein, Stranger in a Strange Land, page 107:

I do not grok all fullness of what I read. In the history written by Master William Shakespeare I found myself full of happiness at the death of Romeo. Then I read on and learned that he had discorporated too soon – or so I thought I grokked. Why?

He freely plucks notions and verbiage from science fiction to describe everything from mountain-related undertakings to political subterfuge – like "grok", a term from Robert Heinlein's Stranger in a Strange Land, to denote intuitive understanding.

(transitive,slang) To fully and completely understand something in all of its details and intricacies.

He groks Perl.

I find it exceedingly doubtful that any person groks quantum mechanics.

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